The figure to the left is from a new paper in Science, When the World’s Population Took Off: The Springboard of the Neolithic Demographic Transition. It reports the findings from 133 cemeteries in the northern hemisphere in regards to the proportion of 5-19 year old individuals. When calibrated to period when agriculture was introduced into a specific region there seems to be a clear alignment in terms of a demographic transition toward a “youth bulge.” Why? A standard model of land surplus explains part of it surely. When farmers settle “virgin land” there is often a rapid “catch up” phase toward the Malthusian limit, the carrying capacity. Another possibility though is that sedentary populations did not need to space their offspring nearly as much as mobile hunter-gatherers. Whatever the details, the facts remain that the data do point to a shift in the age pyramid during this period. The author wonders as to the possible cultural implications of this. There is an a priori assumption that a young vs. old age profile in a society constrains its choices and channels its energies (e.g., think the “baby boom” generation in the USA). A final interesting point is that the authors note that today we are seeing the last gasp of this transition toward large numbers of children, as fertility drops toward replacement all across the world. That too may have some cultural consequences.

Okay…I’m curious. Doesn’t it point not necessarily to a higher proportion of 5-19-year-olds overall, but a higher proportion of *dead* 5-19-year-olds? In other words, this seems to point to an agrarian society being much more dangerous to young humans than the earlier hunter-gatherer societies. I’m thinking more in terms of higher population density leading to more growth of disease that takes down younglings without fully grown immune systems. ?

Peter Ellis

Do mobile hunter-gatherers even have cemeteries, generally? If not, then what evidence are they using for the points they have before the transition?

Justin Giancola

both good points.

bob sykes

I don’t see it. The (hand-drawn?) line is bogus. Take it out and look at the data. There is no trend.

There does seem to be an increase in cemeteries during the neolithic, which makes sense if there are more people around. However since the writers adjusted time to coincide with the start of the local neolithic there could be an error there, too. That is, if they are wrong about the start of the local neolithic, cemeteries might plot left or right of where the chart shows them.

Ian

@4 – looks like a LOESS regression. I haven’t looked at the original paper, but I rather doubt it’s “bogus”. The pre-Neolithic data is a little thin, but just eyeballing it, there looks to be a trend over the first 1000 years of agriculture.

http://blogs.discovermagazine.com/gnxp Razib Khan

#4, if you think LOESS is hand-drawn you should shut up otherwise i might finally make u.

#1, yeah, he elaborates on this. he assumes a malthusian ‘balance.’

#2, i assume cave burial grounds or whatever are being substituted.

DK

Bob is absolutely right. The regression shown is completely bogus. This is scientific equivalent of Hollywood’s “zoom on a low res picture, apply Computer Magic (TM) and get very high res detail back”. LOESS-shmoess. However this line was generated and never mind what smoothing parameters were used, it’s still bogus in that one cannot derive conclusions from its shape the way the author does – there simply isn’t enough data! (The actual paper does not even mention how the line was drawn nor it has anything remotely resembling materials and methods; it does have completely uninformative huge photograph though. I guess different fields have different standards…)

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com